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Back to condensation trails.

  1. Feb 10, 2004 #1
    I used to race with a club called NSRA (www.nsraracing.com) that runs winged sprint cars on asphalt tracks. Every once in a while, especially on the larger tracks and in colder weather, you'd see little condensation vortices (plural vortex) behind the tips of the wings. Even less often one could see a "pocket" of condensation just below the trailing edge of the wing. It kind of looks like a cloud, in a way. What causes that? Is it related to the vortices? I'd like to get pictures, but it happens so abruptly, and usually at night (not camera friendly, when the air is around 40-50 degrees farenheit).
     
  2. jcsd
  3. Feb 10, 2004 #2
    is it kind of like when an airplane is flying?
    [?]
     
  4. Feb 11, 2004 #3

    russ_watters

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    Staff: Mentor

    Its probably a contrail exactly like one created by a plane.
     
  5. Feb 11, 2004 #4
    I suppose it's a contrail, but it's not exactly a trail. I guess it's more like a block of low pressure (sounds like a weather system). I'll see if I can find pictures of the contrails and post them to my site.
     
  6. Feb 12, 2004 #5

    LURCH

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    Yes, it is caused by the drop in pressure, but I've recently been doing a little research which would seem to indicate that this is only the indirect cause. According to everything I've read, air kept at a constant temperature and volume will hold the same amount of water vapor regardless of pressure. So I think this must mean that the drop in pressure causes a drop in temperature, and the drop in temperature is what causes the condensation.

    Although con trails from aircraft can be formed this way, it is rather rare. Usually, when you see a contrail behind an airplane, the cloud is being caused more by the water clinging to the exhaust than by the change in pressure. But if you've evr seen an airshow, you can see that the wings do indeed form little "clouds", which appear to cling to the wing's surface.

    Since you spoke of vortices, I'm assuming you've actually seen rotational motion to some of these clouds. Would I be correct in my supposition that this rotation is outward at the top, inward at the bottom? And does the cloud from the "block of low pressure" form on the underside of the car's wing?
     
  7. Feb 13, 2004 #6
    There is a rotation. If I remember correctly, viewed from the rear, the left side rotates counter-clockwise, and the right rotates cloclwise. The cloud forms on the underside of the wing, where it seems the air is moving the fastest. The angle of attack on the wing of a sprint car is relatively high compared to an airplane wing. I have seen the condensation on the trailing edge of an airplane as it was taking off. The best view of it from an airliner is right behind the wing. You also get to watch the flaps, spoilers and airbrakes work, which is a marvel of physics if you ask me.
     
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